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PubMed1988

Origin of sympathetic and sensory innervation of the elbow joint in the rat: a retrograde axonal tracing study with wheat germ agglutinin conjugated horseradish peroxidase.

After injection of wheat germ agglutinin conjugated horseradish peroxidase (WGA-HRP) into the elbow joint of adult rats, labeled neurons were found in the stellate and the T2-T4 ganglia of the ipsilateral sympathetic trunk, and also in dorsal root ganglia at the C4-T4 levels. Most labeled sympathetic cells, 90% or more, were located in the stellate ganglion. The sensory innervation to the joint originated mainly from the dorsal root ganglia at the levels of C7-T1.

Afferent Pathways↗
PubMed1991

The Edinger-Westphal nucleus: sources of input influencing accommodation, pupilloconstriction, and choroidal blood flow.

This study used neuroanatomical techniques to investigate sources of afferents to the Edinger-Westphal nucleus (EW) of the pigeon. The EW contains the parasympathetic preganglionic neurons that, by way of the oculomotor nerve, project to the ciliary ganglion (Narayanan and Narayanan, '76; Lyman and Mugnaini, '80). The ciliary ganglion, in turn, innervates the internal musculature of the eye; the ciliary body, the iris sphincter muscle, and the smooth muscle of choroidal blood vessels (Marwitt et al., '71; Pilar and Tuttle, '82). In the bird, the neurons in the ciliary ganglion that innervate the iris sphincter muscle and the ciliary body receive input specifically from cells in the lateral EW (EWl), whereas those that innervate choroidal blood vessels receive input from cells in the medial EW (EWm) (Reiner et al., '83). Thus neurons in the EWl mediate pupilloconstriction and accommodation, whereas neurons in the EWm modulate choroidal blood flow. To study the afferents to EW, injections of horseradish peroxidase (HRP) were placed in this nucleus. These injections resulted in labeled cells in the area pretectalis, a retinorecipient pretectal nucleus and the suprachiasmatic nucleus, a retinorecipient hypothalamic nucleus. We have previously identified both these areas as being sources of afferents to EW (Gamlin et al., '82, '84). In addition, these HRP injections into EW resulted in labeled cells in the medial mesencephalic reticular formation (MRF) lateral and ventral to the oculomotor nucleus and in a localized area of the rostral lateral mesencephalic reticular formation (LRF) dorsolateral to nucleus subpretectalis. Injections of tritiated amino acids into the MRF labeled the entire EW, while such injections into the LRF labeled only the lateral EW. Both of these projections were predominantly contralateral. This study has identified the sources of two previously undocumented inputs to the avian EW. Both sources of input, the MRF and rostral LRF, receive afferents from visuomotor areas of the telencephalon and visual structures in the midbrain. The MRF input to EW could have either direct or modulatory influences on pupil diameter, accommodation, and choroidal blood flow. The LRF input to EW could play a role in controlling accommodation and possibly the pupillary near response.

Afferent Pathways↗
PubMed1991

Heterogeneous visceral nerve changes in acrylamide intoxication.

A variety of visceral nerves were studied by intermediate filament immunocytochemistry in rats intoxicated with acrylamide. In such animals, oesophageal and diaphragmatic motor end-plates were invaded and deformed by neurofilament protein-like material, while afferent fibres of diaphragmatic neuromuscular spindles and myelinated sensory fibres of the iris showed striking terminal accumulation of similar material. Conversely, the rich population of thin afferent fibres of the iris showed no obvious abnormality, while pre-terminal changes were seen along the extrinsic nerve fibres supplying the cornea and myenteric ganglia. Multiple lesions were demonstrated in gut nerves of acrylamide-treated rats, while scattered "enteric glial cells" showed abnormally coarse morphology and a striking increase in glial fibrillary acidic protein immunoreactivity. A distinct, delicately varicose appearance was revealed by neurofilament protein-immunostaining in bladder nerve fibres of normal rats, which was changed to one of coarse dilations by acrylamide. In conclusion, apparently selective changes were found along different types of axons, indicating marked heterogeneity in cytoskeletal organisation among visceral nerves. Taken together with the proposed inhibition by acrylamide of neurofilament proteins degradation, the above findings may suggest a non-uniform distribution of neurofilament degradation sites along distal regions of different axons.

Acrylamide↗
PubMed1990

Potassium channel blockade differentially affects the relative refractory period of frog afferent terminals and axons.

1. The effects of potassium channel blockade on afferent axons and terminal regions in frog dorsal roots and spinal cords, respectively, were investigated in vitro. 2. A condition-test (C-T) protocol was used to assess the population relative refractory period. Characteristics of main axons were evaluated by stimulation at the proximal end of transected dorsal roots (DR). Characteristics of terminal regions were tested by stimulation at the base of the dorsal horn (DH). 3. DH recovery of excitability was delayed by low concentrations of 4-aminopyridine (4-AP) and tetraethylammonium (TEA) alone or combined. The same treatments did not affect recovery to DR stimulation. 4. DH recovery of excitability was not delayed by solutions suppressing terminal calcium influx. 5. We conclude that sensitivity of the relative refractory period to potassium channel blocking agents differs between main axons and axon terminal regions. This may indicate differences between axon terminals and main axons in the mechanism of action potential repolarization. 6. We hypothesize that rapid action potential repolarization by pharmacologically sensitive potassium channels in presynaptic terminal regions keeps terminal action potentials short. Terminal action potential brevity would limit calcium influx, thus preventing terminal calcium overload but contributing to transmission failures at spinal synapses.

4-Aminopyridine↗
PubMed2001

The Deoxyxylulose Phosphate Pathway for the Biosynthesis of Plastidic Isoprenoids: Early Days in Our Understanding of the Early Stages of Gibberellin Biosynthesis.

The identification of a novel pathway for isopentenyl diphosphate synthesis by Rohmer, Arigoni and colleagues in the early 1990's has led to a reappraisal of terpenoid biosynthesis in many organisms. It is now apparent that in plants there are two biosynthetic routes to isopentenyl diphosphate-the classical mevalonate pathway in the cytosol and the deoxyxylulose phosphate pathway in plastids. Sesquiterpenoids and sterols are predominantly synthesized in the cytosol by the mevalonate pathway whereas monoterpenoids, diterpenoids, the phytol side-chain of chlorophyll, carotenoids, and the nonaprenyl side-chain of plastoquinone-9 are synthesized within plastids by the deoxyxylulose phosphate pathway. Our assumptions that the early stages of gibberellin biosynthesis are plastid-localized has led to several attempts to demonstrate that the deoxyxylulose phosphate pathway is the biosynthetic route to gibberellins. Although definitive evidence is still not available there is a growing body of evidence, mostly from transgenic plants and from the use of the inhibitor, fosmidomycin, that gibberellins are synthesized from deoxyxylulose phosphate-derived isopentenyl diphosphate. However, there is evidence that a small amount of cross-talk between the two pathways may occur, implying that the pathways are not totally autonomous. Implications for the regulation of the early stages of gibberellin biosynthesis are discussed.

Journal Article↗
PubMed2002

Distribution, immunohistochemical characteristics and nerve pathways of primary sensory neurons supplying the porcine vas deferens.

The present study investigated: (1) the distribution and chemical coding of primary sensory neurons supplying the vas deferens in juvenile pigs by the use of retrograde tracing combined with double-labelling immunofluorescence, (2) nerve pathways from dorsal root ganglia (DRG) to the vas deferens by means of denervation procedures involving transection of the hypogastric or pelvic nerve combined with a retrograde tracing method, and (3) possible interactions of the substance P (SP)/calcitonin gene-related peptide (CGRP)-immunoreactive varicose nerve fibres on vas deferens projecting neurons (VDPN) in the anterior pelvic ganglion (APG). The vast majority of VDPN were found mainly in the lumbar L2, L3 and sacral S2, S3 pairs of DRG and showed a clear ipsilaterally organized projection pattern. Immunohistochemistry revealed that most of these neurons contained SP and/or CGRP, occasionally coexpressed with galanin. Interestingly, pronounced differences in the expression of SP and/or CGRP were observed between the lumbar and sacral VDPN in that most of the lumbar but less than half of the sacral neurons stained for these peptides. Denervation experiments showed that the neurons located within the lumbar DRG project through the ipsilateral hypogastric nerve, whereas those found within the sacral DRG send their processes through the ipsilateral and contralateral pelvic nerve. In the nerve-lesioned animals, especially in those with the hypogastric nerve cut, a dramatic reduction in the number of SP and/or CGRP-containing nerve terminals surrounding the efferent VDPN within the APG was observed. This study has disclosed the distribution and, for the first time, chemical coding and nerve pathways of vas deferens-projecting primary sensory neurons in a mammalian species, the pig. The results obtained also provide some novel information about the possible morphological and functional relationship between vas deferens-projecting primary sensory and pelvic efferent nerve cells.

Afferent Pathways↗
PubMed1980

Functional properties of lumbar preganglionic neurones.

Lumbar preganglionic neurones projecting through WRL2 and L3 to lumbar ganglia caudal to L4 were investigated for those functional properties which are typical for postganglionic vasoconstrictor neurones supplying muscle and skin and for post ganglionic sudomotor neurones. The properties tested were the cardiac rhythmicity of the activity and the reactions to systemic hypoxia, to noxious stimulation of skin and (in part of the experiments) to vibrational stimuli. Furthermore, resting activity and conduction velocities of the asons were measured. 426 neurones were investigated. 311 (73%) of them were silent and could -- as far as tested -- not be excited by the afferent stimuli used. The conduction velocities of the axons of these neurones ranged from 0.5 to about 16 m/sec. 115 neurones had resting activity of 0.1--4.6 impulses/sec. The conduction velocities of their axons ranged from 0.5 to about 12 m/sec. 80 preganglionic neurones with resting activity were classified on the basis of the reflexes in these neurones to afferent stimuli. Preganglionic neurones reacting like postganglionic vasoconstrictor neurones to muscle (excited by systemic hypoxia and/or by noxious stimulation of skin; with cardic rhythmicity) were classified as type 1 neurones (26 from 80 neurones tested). The resting activity of these neurones was 1.8 +/- 1.3 impulses/sec (mean +/- 1 S.D.). Their axons conducted with 3.9 +/- m/sec. Preganglionic neurones reacting like the majority of the postganglionic vasoconstrictor neurones to hairy and hairless skin (inhibited by systemic hypoxia and/or noxious cutaneous stimuli) were classified as type 2 neurones (48 from 80 neurones investigated). In 40% of these neurones the activity had cardiac rhythmicity. The resting activity was 0.9 +/- 0.6 impulses/sec. The distribution of the conduction velocities of the axons of these neurones was bimodal. They conducted on the average with 1.3 +/- 0.6 m/sec and 6.6 +/- 1.1 m/sec respectively. A few neurones were found (6 from 80 neurones) which were activated by vibrational stimuli (activation of Pacinian corpuscles by tapping on the hindfoot). Since this type of activation is typical for postganglionic sudomotor neurones they were classified as type 3 neurones. The activity of these neurones had no cardiac rhythmicity. Indirect measurements of the conduction velocities of pregnanglionic axons converging onto postganglionic neurones supplying skeletal muscle and hairy skin yielded values which were statistically not different from the conduction velocities of the axons of type 1 and type 2 neurones respectively. These measurements support the classification into type 1 and type 2 preganglionic neurones. The implications of this study are discussed.

Action Potentials↗
PubMed1984

Possible projections from regions of paraventricular and supraoptic nuclei to the spinal cord: electrophysiological studies.

The existence of monosynaptic connections between neurons in the paraventricular nucleus (PVN) of the hypothalamus and the intermediolateral cell column (ILC) of the spinal cord was studied by electrophysiological techniques in chloralose-anesthetized cats. Sympathetic preganglionic discharges (recorded from the 2nd or 3rd thoracic white ramus) were evoked by microstimulation of certain regions in or near the PVN with short train of pulses and below 50 microA current. By recording responses of 'identified' and 'non-identified' neurosecretory cells in the PVN and supraoptic nucleus (SON) to stimulation of the ILC of the thoracic cord, it was possible to identify antidromically evoked action potentials in 9 out of 297 neurons tested. Among them, 2 neurons were also antidromically excited by the pituitary stalk stimulation, 5 were orthodromically excited by the same stimulus and the remaining 2 were not excited by the stalk stimulation. Our results indicate that some PVN neurons, though small in number, send axons directly to the ILC of the cord, and that a very few neurons among these also send their axons to the pituitary gland.

Afferent Pathways↗
PubMed1986

The presence of vasoactive intestinal polypeptide-like immunoreactive structures projecting from the myenteric ganglion of the stomach to the celiac ganglion revealed by a double-labelling technique.

The gastrofugal vasoactive intestinal polypeptide (VIP)-like immunoreactive (VIPI) structures in the rat were examined by the combined use of immunocytochemistry and retrograde tracing. Injection of biotin-wheat germ agglutinin into the celiac ganglion labeled many neurons in the myenteric ganglion of the stomach. Simultaneous staining with antiserum against VIP showed that some of these neurons are VIPI-positive. These findings indicate that VIPI neurons in the myenteric ganglion of the rat stomach project to the celiac ganglion.

Animals↗
PubMed1987

Central nervous system actions of beta-endorphin on gastric acid secretion.

We assessed the central nervous system (CNS) actions of beta-endorphin on gastric acid secretion in awake dogs. Synthetic beta-endorphin (0.2-2.0 nmol X kg-1), but not Leu- or Met-enkephalin, microinjected into the third cerebral ventricle, significantly (P less than 0.01) decreased gastric acid secretion stimulated by pentagastrin. beta-Endorphin given intracerebroventricularly inhibited gastric acid secretion following 2-deoxy-D-glucose (P less than 0.01), but not after stimulation with histamine. Intravenous administration of beta-endorphin did not inhibit gastric acid secretion. beta-Endorphin decreased gastric acid secretion but not the concomitant release of gastrin stimulated by a 200-ml liquid meal containing 8% peptone. Pretreatment of the animals with the opioid antagonist, naloxone, prevented the gastric inhibitory effect of beta-endorphin. Furthermore, either ganglionic blockade with chlorisondamine or truncal vagotomy completely abolished the gastric inhibitory action of beta-endorphin. These findings indicate that beta-endorphin, but neither Leu- nor Met-enkephalin, acts within the CNS to inhibit gastric acid secretion in awake dogs. beta-Endorphin-induced inhibition of gastric acid secretion is mediated by an opiate-dependent pathway and by the autonomic (parasympathetic) nervous system.

Animals↗
PubMed1988

Spinal projections of renal afferent nerves in the rat.

This study was designed to describe renal afferent information with respect to its intraspinal projections, convergence with cutaneous inputs, ascending projections, and modulation by descending fiber tracts. Extracellular recordings were made from neurons in the spinal gray while electrically stimulating the renal nerves in chloralose-anesthetized, artificially ventilated rats. Almost all neurons (n = 119) were spontaneously active. Some responses consisted of high-frequency bursts while others consisted of fewer than 6 action potentials. Response onset latencies to renal nerve stimulation were consistent with activation by thinly myelinated or unmyelinated afferents. Several neurons in deeper laminae were inhibited by stimulation of renal afferents. Most neurons were located in laminae IV and V. Some were located in laminae I, VII and VIII. All neurons were located at spinal levels T10 to L1. Most neurons responded to both noxious and non-noxious mechanical cutaneous stimuli from relatively large receptive fields on the ipsilateral flank. Response latencies to cutaneous electrical stimulation were shorter than those to renal nerve stimulation. Neurons in intact and spinally transected rats responded with similar onset latencies and durations to renal nerve stimulation. However, neurons in spinally transected rats exhibited prolonged responses to cutaneous stimulation. Axons of 25% of the neurons projected through the cervical spinal cord in the ventrolateral funiculus. They had conduction velocities of 12-32 m/s. These data provide the first electrophysiological description of spinal projections of renal afferent fibers in the rat.

Afferent Pathways↗
PubMed1987

Fear-potentiated startle using an auditory conditioned stimulus: effect of lesions of the amygdala.

The effect of lesions of the amygdala on fear-potentiated startle using an auditory conditioned stimulus (CS) was evaluated, after replicating and extending previous findings that a tone is an effective CS for fear-potentiated startle. Rats received 10 tone-shock pairings on 2 successive days. At 24-48 hr following training, they received bilateral electrolytic lesions of the central nucleus of the amygdala or sham operations, and then were tested for fear-potentiated startle 4-5 days later. Lesions of the amygdala impaired fear-potentiated startle using an auditory CS, consistent with the previous findings using a visual CS. These data indicate that the effect of lesions of the amygdala on fear-potentiated startle is not specific to one sensory modality, consistent with the hypotheses that the amygdala is involved in processing multimodal information related to conditioned fear, or is part of an output pathway for motor and autonomic expressions of conditioned fear.

Acoustic Stimulation↗
PubMed1989

The stimulatory effect of nicotine on vagal pulmonary C-fibers in dogs.

Our recent studies suggested that a nicotine-induced stimulation of afferent vagal C-fibers in the lungs was involved in eliciting the immediate cardiorespiratory responses to inhaling cigarette smoke. To examine this possibility, afferent impulses were recorded from vagal pulmonary C-fibers in 16 anesthetized, open-chest and artificially ventilated dogs, before and after four separate doses of nicotine (2.5, 5, 10 and 20 micrograms/kg) were injected into the right atrium. The base-line activity did not change after injection of isotonic saline. In contrast, nicotine stimulated 24 of 29 C-fibers: a burst of discharge was evoked immediately (1-2 sec) after the injection and usually lasted 3-8 sec. The peak responses of these pulmonary C-fibers to nicotine injections showed a dose-dependent relationship. In 17 C-fibers tested, the responses evoked by right atrial injection of 10 micrograms/kg of nicotine were similar to those evoked by delivery into the lungs of a single breath of smoke generated from cigarette with a high-nicotine content. Based upon these results, we conclude that nicotine alone stimulates vagal pulmonary C-fibers in a dose-dependent manner and this stimulant action of nicotine may play a part in eliciting the immediate reflex cardiorespiratory responses to inhalation of cigarette smoke.

Afferent Pathways↗